The invention relates particularly to a method for reducing the energy consumption of a motor vehicle having at least one electric on-board power supply system to which at least one electric consuming device is connected.
The number of electric consuming devices in motor vehicles has increased considerably. In order to reduce the CO2 emission in the vehicle, hydraulically operating consuming devices are being replaced by electric consuming devices. Thus, as required, for example, an electric steering system (EPS) replaces the hydraulic steering of the motor vehicle. However, such electric consuming devices make high power demands on the vehicle power supply system for a short time. This results in a high demand on the overall stability of the vehicle power supply system. In particular, in the case of high demands occurring for short periods of time, a sufficiently high electric voltage or electric power has to be made available.
It is an object of the invention to provide a method of implementing an efficient on-board power supply system and, in addition, permitting the reduction of the energy consumption of a motor vehicle.
This object is achieved by a method and an on-board power supply for reducing the energy consumption of a motor vehicle having at least one electric consuming device connected to the on-board power supply. The voltage level and/or power level of the electric on-board power supply system is kept at a first, low level during a first operating condition of the motor vehicle. The voltage level and/or power level of the electric on-board power supply system is temporarily raised to a second, higher level in a second operating condition of the motor vehicle, and a driving situation detection device provided in the vehicle recognizes a largely directly imminent special driving situation as a result of the preceding behavior of the driver when controlling the vehicle and/or of the vehicle in advance and causes the voltage level and/or the power level of the electric power supply system to be temporarily raised to the second, higher level. Advantageous further developments of the invention are described herein.
An essential aspect of the invention consists of the fact that the voltage level and/or power level of the electric on-board power system is held at a first, low level in a first operating condition of the motor vehicle. In this first operating condition, the energy consumption and therefore the CO2 emission are reduced.
In a second operating condition, the voltage level and/or the power level of the electric on-board power supply system is temporarily raised to a second, higher level. In this second operating condition, especially “power-hungry” consuming devices or loads are supplied with a sufficiently high electric voltage and/or electric power from the on-board power supply system. These consuming devices will then react in the expected, in particular, comfortable fashion. If, for example, during a turning maneuver or during a turning operation, an electric steering system is operated only at the low voltage level and/or power level of the first operating condition, the steering will be sluggish, which causes the driver to feel insecure, particularly during a turning maneuver, which as a rule should be carried out rapidly, and therefore results in a clear loss of comfort.
In order to initiate the second operating condition sufficiently early but, for reasons of a low CO2 emission in the first operating condition, only if required, according to the invention a driving situation detection device provided in the vehicle will recognize a largely directly imminent special driving situation, based on the driver's preceding behavior when steering the vehicle, ahead of time and cause the voltage level and/or power level of the electric on-board power supply system to be temporarily raised to the second, higher level. “Sufficiently early” preferably means early enough for the second operating condition to be set at the point in time of the start of the expected turning operation. “Temporarily” preferably means that the time duration is calculated such that the imminent driving situation can be mastered securely and without a loss of comfort by the driver with the participation of the corresponding electric consuming devices.
In an embodiment of the invention, it is provided that the electric consuming device is an electrically operated steering system of the motor vehicle, and the largely directly imminent special driving situation is a turning operation. This is a driving situation in which a low electric voltage may become noticeable to the driver in a particularly unpleasant fashion.
In a further development of the invention, it is provided that the position of the accelerator or gas pedal is detected by the driving situation detection device, and the electric voltage and/or the electric power is increased when the accelerator or gas pedal is largely in its rest position and at least one further driving situation occurs. This is characteristic of an imminent turning operation and, therefore, particularly informative with respect to an early detection of a turning operation.
In a further development of the invention, it is provided that the acceleration and the speed of the vehicle are detected by the driving situation detection device, and the electric voltage and/or power is increased when the acceleration of the vehicle is negative, the speed falls below a predetermined threshold value, and at least one further driving situation occurs. This is also characteristic of an imminent turning operation and supplies an important indication of an imminent turning operation.
In another embodiment of the invention, the steering angle of the electric steering system of the vehicle is detected by the driving situation detection device. The electric voltage and/or power is increased when the absolute value of the steering angle is greater than a predetermined threshold value and at least one further driving situation occurs. This may be an indication that the driver is starting to swerve and/or is starting a turning maneuver. Since many drivers swerve before a turning operation, this may possibly be another helpful criterion for recognizing an imminent turning operation sufficiently early.
In another embodiment of the invention, it is provided that the steering angle of the electric steering system of the vehicle is detected by the driving situation detection device, and the electric voltage and/or power is increased when the absolute value of the steering angle is greater than a predetermined speed-dependent steering threshold or steering angle threshold and at least one additional driving situation occurs. If the driver does not swerve before a turning operation, this characteristic of an imminent turning operation can replace the “swerve criterion” and increase the reliability of the prediction of an imminent turning operation.
In a further development of the invention, it is provided that the driving situation detection device checks whether the brake pressure is higher than a predetermined brake pressure or a tolerance pressure and, in addition, checks whether the speed is lower than a predetermined acceleration-dependent speed value or a dynamic turning threshold. This results in a further increase in the reliability of the prediction of a turning operation.
In addition, the invention provides an on-board power supply system of a motor vehicle, which has a program-controlled driving situation detection device implementing the method according to the invention. Furthermore, a program-controlled driving situation detection device is provided, which implements a method according to the invention or causes its implementation.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.